Method and apparatus for limiting ring current in short circuit between adjacent partial windings of regulating winding by increasing leakage impedance in regulating winding

ABSTRACT

Apparatus for regulating an electric voltage in at least one of electric supply networks and consumer units. The apparatus includes a regulating transformer arranged between a network node and at least one end consumer. The regulating transformer utilizes a primary winding and a regulating winding which includes switchable partial windings and a high leakage impedance. The transformer conducts a nominal current. A transfer switch switches the partial windings of the regulating transformer. Adjacent tappings of the partial windings are adapted to short circuit such that, in an event of the short circuit, the high leakage impedance limits a ring current which results from the short circuit to an order of magnitude of the nominal current. The regulating transformer produces both an increase in voltage and a decrease in voltage at the end consumer. This abstract is not intended to define the invention disclosed in the specification, nor intended to limit the scope of the invention in any way.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of U.S. applicationSer. No. 10/111,808 filed Apr. 29, 2002, the disclosure of which isexpressly incorporated by reference herein in its entirety, whichapplication is a U.S. National Stage of International Application No.PCT/AT00/00284 filed Oct. 31, 2000 and claims priority under 35 U.S.C. §119 of Austrian Patent Application No. A 1838/99 filed Nov. 2, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a method for regulating the electricalvoltage in electrical supply networks and/or consumer units and a devicefor carrying out said method.

[0004] 2. Discussion of Background Information

[0005] It is generally known to carry out voltage regulation only in thecentral network nodes of high or medium voltage networks. Furthertransformation to low-voltage level normally cannot be regulated underload. This network structure is oriented towards the central powersupply and has the disadvantage that voltage fluctuations caused by achange in node cannot be adjusted for between the network node and theend consumer. Thus, the exploitable transfer capacity of the networkcomponents downstream from the network nodes is limited by the drop involtage rather than by thermal strength.

[0006] Regulating transformers are provided for voltage regulation ofthe networks in the central network nodes. Regulating transformers areused for incremental voltage regulation in electrical networks bychanging the transformer ratio. For this purpose, regulatingtransformers are fitted with regulating windings with tappings, whichcan be switched under load. During the switching processes, the loadcurrent must not be interrupted and the winding step between therelevant tappings must not be shorted. The second requirement resultsfrom the fact that during each switching process between twoneighbouring tappings they are necessarily briefly connected to eachother due to the first requirement, so that there is a ring currentequivalent to the transformer short-circuit current between the switchand the relevant winding, the action of which the transformer is unableto withstand, especially during periodical operation. This transformershort-circuit current is relatively high, since the internal resistanceof the transformer is normally small. Furthermore, the incrementalswitches of the transformers would have to be coordinated with theperiodical switching of these high short-circuit currents.

[0007] For the above reasons, the switching process in the incrementalswitch of the transformer does not happen directly but rather inmultiple stages, whereby transition impedances are briefly switched intothe circuits of the tappings during the switching process, limiting thering current. In Europe, ohmic transition impedances are common, and inAmerica inductive transition impedances are common. For multi-phaseswitching, a number of switching principles are applied that are namedafter the vector diagrams of the switching processes. For example wespeak of symmetrical or asymmetrical flag switching.

[0008] The disadvantage of the measures used so far to limit the ringcurrent is that they result in complex transition principles and requirecomplex designs of the regulating transformers.

SUMMARY OF THE INVENTION

[0009] The aim of this invention is therefore to create a method of thetype mentioned above that on the one hand avoids the above disadvantagesand on the other hand allows or guarantees a better and more efficientuse of the existing networks through a new field of voltage regulationapplication that is closer to the consumer. The problem is solved bythis invention.

[0010] The method in accordance with the invention is characterised bythe fact that a regulating transformer with a transfer switch thatswitches the partial windings of the regulating transformer is insertedbetween a network node of the supply network and/or the consumer unitand at least one end consumer, whereby the regulating transformer has ahigh leakage impedance that limits the ring current to the order ofmagnitude of the nominal current in the case of a short circuit betweenadjacent tappings.

[0011] With this invention it is for the first time possible to carryout voltage regulation in networks or consumer units in proximity to theconsumer and on the basis of regulating transformers that have anincreased impedance of the regulating windings, so that a simplifiedstep switch without transition impedances can be used.

[0012] With the liberalisation and decentralisation of electric powersupply and due to the higher bi-directional work-load of the networks,the voltage differences between heavy-duty consumption, low duty andpossibly the power supply will become greater on the consumer side. Tomaintain the voltage there should therefore be voltage regulation at thelevel of the low voltage or possibly at the level of the medium voltageas an economic solution.

[0013] It is a further aim of the invention to provide a device forcarrying out this method, which has a simple and robust structure andwhich can be manufactured economically.

[0014] According to a special feature of the invention, the device forcarrying out the method is characterised by the fact that the regulatingtransformer is designed as a longitudinal regulator with a differentialcapacity that is proportional to the voltage difference that is to beregulated. In accordance with the invention, longitudinal regulators forvoltage maintenance are therefore provided in the network spurs, whichdo without the known and currently common transition impedances of thestep switch and thus the resistance contacts. This is primarily possiblebecause the voltage regulation is carried out at low-duty networkpoints. Even an increased impedance of such a longitudinal regulatorwill only have a marginal effect on the total internal resistance of thenetwork.

[0015] The need for transition impedances results from the fact that forreasons of voltage maintenance the internal network resistance andshort-circuit impedance of regulating transformers is much lower thanthe load impedance, so that the short-circuit currents are significantlyhigher than the operating currents.

[0016] If the short-circuit impedance of the regulator winding isincreased, e.g. by widening the leakage gap, so that the ring circuit inthe case of a short circuit between adjacent tappings is of the order ofmagnitude of the nominal current, the additional transition impedancesare not required and the step switch is simplified into a normaltransfer switch.

[0017] The regulating winding can be designed both as a concentricwinding and as a flat coil winding with the relevant tappings. Thisprinciple can be applied both to full transformers with regulatingwinding and to one-coil transformers for longitudinal regulation. Theregulating winding can be connected to the secondary winding or primarywinding both via one end of the winding and via a tapping.

[0018] Since the device is suitable for the voltage regulation ofnetwork spurs, its capacity based on the transitional capacity lieswithin a range of a some 10 kVA to some 10 MVA.

[0019] In a further embodiment of the invention, the transfer switch isa load switch without resistance contact and with only main contacts. Asalready shown above, such a load transfer switch offers an economicalsolution.

[0020] In a further embodiment of the invention, the transfer switch isa load selector without resistance contacts. This embodiment of thetransfer switch also has an extremely simple structure and can beproduced economically.

[0021] In further embodiments of the invention, the transfer switch canalso be designed on the basis of a multi-phase camshaft controller or achain of relays or contactors or a chain of electronic switches, inparticular semiconductor switches. These embodiments of the transferswitch also have a simple structure and are extremely reliable in robustoperations.

[0022] The present invention is directed to a method to regulateelectric voltage in at least one of electric supply networks andconsumer units with a regulating transformer located between a networknode of the at least one of the electric supply networks and theconsumer units and at least one end consumer, in which the regulatingtransformer has switchable partial windings. The process includesswitching the partial windings of the regulating transformer with atransfer switch. In this manner, in an event of a short circuit betweenadjacent tappings of the partial windings, the regulating transformerhas a high leakage impedance that limits ring current to an order ofmagnitude of a nominal current.

[0023] The present invention is directed to an apparatus arranged toperform the above-noted method.

[0024] According to the invention, the transfer switch can include aload switch without resistance contacts. Further, the load switch mayinclude only main contacts.

[0025] In accordance with another feature of the invention, the transferswitch may include a load selector, and the load selector can bearranged without resistance contacts.

[0026] Further, according to features present invention, the transferswitch may include a multi-phase camshaft controller.

[0027] According to still another feature of the instant invention, thetransfer switch can include a chain of one of relays and contactors.

[0028] In accordance with yet another feature of the invention, thetransfer switch may include a chain of electronic switches. The chain ofelectronic switches may include semiconductor switches.

[0029] The present invention is directed to an apparatus to regulateelectric voltage in at least one of electric supply networks andconsumer units that includes a regulating transformer, positionedbetween a network node of the at least one of the electric supplynetworks and the consumer units and at least one end consumer, thatincludes a plurality of switchable partial windings, and a transferswitch arranged to selectively contact tappings of the switchablepartial windings. The regulating transformer includes a leakage gap suchthat, in the event of a short circuit between adjacent tappings of theswitchable partial windings, the regulating transformer has a highleakage impedance that limits ring current to an order of magnitude of anominal current.

[0030] The invention also provides for a method of regulating anelectric voltage in a network node of at least one of electric supplynetworks and consumer units, wherein the method comprises arranging aregulating transformer between the network node and at least one endconsumer, wherein the regulating transformer comprises a main windingand a regulating winding which includes switchable partial windings anda high leakage impedance, conducting a nominal current, switching thepartial windings of the regulating transformer with a transfer switch,and short circuiting adjacent tappings of the partial windings, whereinthe high leakage impedance limits a ring current to an order ofmagnitude of the nominal current during the short circuiting, andwherein the regulating transformer produces both an increase in voltageand a decrease in voltage at the end consumer.

[0031] The regulating transformer may be a longitudinal regulator. Theregulating winding may be one of a concentric winding and a flat coilwinding. The regulating transformer may be one of a full transformer anda one-coil transformer. The regulating winding may be connected to themain winding. The regulating transformer may further comprise asecondary winding and the regulating winding may be connected to one ofthe main winding and the secondary winding. The regulating transformermay be adapted to regulate voltages in the range of 10 kVA and 10 MVA.

[0032] The invention also provides for an apparatus for regulating anelectric voltage in at least one of electric supply networks andconsumer units, wherein the apparatus comprises a regulating transformerarranged between a network node and at least one end consumer. Theregulating transformer comprises a main winding and a regulating windingwhich includes switchable partial windings and a high leakage impedance.The regulating transformer conducts a nominal current. A transfer switchswitches the partial windings of the regulating transformer. Adjacenttappings of the partial windings are adapted to short circuit such that,in an event of the short circuit, the high leakage impedance limits aring current which results from the short circuit to an order ofmagnitude of the nominal current, and the regulating transformerproduces both an increase in voltage and a decrease in voltage at theend consumer.

[0033] The regulating transformer may be a longitudinal regulator. Theregulating winding may be one of a concentric winding and a flat coilwinding. The regulating transformer may be one of a full transformer anda one-coil transformer. The regulating winding may be connected to themain winding. The regulating transformer may further comprise asecondary winding and the regulating winding may be connected to one ofthe main winding and the secondary winding. The regulating transformermay be adapted to regulate voltages in the range of 10 kVA and 10 MVA.

[0034] The invention also provides for a method of regulating anelectric voltage in a network node of at least one of electric supplynetworks and consumer units, wherein the method comprises arranging aregulating transformer between the network node and at least one endconsumer, wherein the regulating transformer comprises a main windingand a regulating winding which includes switchable partial windings,conducting a nominal current, switching the partial windings of theregulating transformer with a transfer switch, short circuiting adjacenttappings of the partial windings, and increasing a leakage impedance ofthe regulating winding, wherein the leakage impedance limits a ringcurrent to an order of magnitude of the nominal current during the shortcircuiting.

[0035] The increasing may result from a widened leakage gap in theregulating transformer. The regulating transformer may produce both anincrease in voltage and a decrease in voltage at the end consumer. Theregulating transformer may be a longitudinal regulator. The regulatingwinding may be one of a concentric winding and a flat coil winding. Theregulating transformer may be one of a full transformer and a one-coiltransformer. The regulating winding may be connected to the mainwinding. The regulating transformer may further comprise a secondarywinding and wherein the regulating winding is connected to one of themain winding and the secondary winding. The regulating transformer maybe adapted to regulate voltages in the range of 10 kVA and 10 MVA.

[0036] The invention also provides for an apparatus for regulating anelectric voltage in at least one of electric supply networks andconsumer units, wherein the apparatus comprises a regulating transformerarranged between a network node and at least one end consumer. Theregulating transformer comprises a main winding and a regulating windingwhich includes switchable partial windings and a widened leakage gap.The regulating transformer conducts a nominal current. A transfer switchswitches the partial windings of the regulating transformer. Adjacenttappings of the partial windings are adapted to short circuit such that,in an event of the short circuit, the widened leakage gap limits a ringcurrent which results from the short circuit to an order of magnitude ofthe nominal current. The regulating transformer produces both anincrease in voltage and a decrease in voltage at the end consumer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The invention is explained in more detail on the basis of theembodiment illustrated in the figure. The figures show:

[0038]FIG. 1 a basic sketch of the arrangement of a one-coil transformer

[0039]FIG. 2 a basic sketch of the arrangement of a full transformer

[0040]FIG. 3 a transfer switch based on contactors, and

[0041]FIG. 4 a transfer switch based on semiconductors.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0042] By way of introduction, it is noted that in the describedembodiment the same parts and the same states are allocated the samereference numbers and the same component names, whereby the disclosurescontained throughout the description can be applied by analogy to thesame parts and the same states with the same reference numbers or samecomponent names. Moreover, individual features from the embodimentillustrated can represent independent solutions according to theinvention in themselves.

[0043]FIG. 1 shows a device for regulating the electric voltage betweenone network node 1—represented by the arrow—and one end consumer 2—alsorepresented by an arrow—whereby a regulating transformer 3 in the formof a one-coil transformer is provided for regulating the voltage. Thisone-coil transformer has a regulating winding with partial windings 4.The regulating winding is connected to the primary winding 6 of theone-coil transformer via a tapping 5, for example via a middle tapping.This allows both an increase and a decrease in voltage on the consumerside. The tappings 5 of the regulating winding are optionally connectedwith the output to the end consumer 2 via a transfer switch 7. Thetransfer switch 7 is controlled either via the control unit 8 withoutregulation or via a voltage controller 10 with regulation. Thetransitions are made in steps by closing a break adjacent to a closedbreak and then opening the original break. This allows the voltage onthe consumer side to be increased or decreased. In addition, anintegrated overvoltage protection 11 can be provided on the side of theend consumer 2.

[0044] To increase the short-circuit impedance of the regulatingwinding, the regulating transformer 3 in the embodiment as a one-coiltransformer has a widened leakage gap 9. Through this increase inleakage impedance, the ring current is limited to the order of magnitudeof the nominal current in the case of a short circuit.

[0045] In FIG. 2 the device for regulating the electric voltage is againarranged between a network node 1 and an end consumer 2, whereby aregulating transformer 3 in the embodiment of a full transformer isprovided for regulation. Thereby, the connection between the regulatingwinding and the partial windings 4 is provided via one end of thesecondary winding of the regulating transformer 3. A transfer switch 7with control unit 8 is again provided at the partial windings 4. Toincrease the leakage impedance, the regulating transformer 3 again has awidened leakage gap 9. The leakage impedance of the secondary winding 14is not increased.

[0046] The transfer switch 7 is designed as a multi-phase camshaftcontroller and corresponds with the tappings 5 of the partial windings4.

[0047] As in the embodiment shown in FIG. 1, the regulating transformer3 is designed as a longitudinal regulator and has a differentialcapacity that is proportional to the voltage difference that is to beregulated.

[0048] In accordance with FIG. 3, the partial windings 4 with theirtappings 5 are connected with a series of contactors, which carry outthe voltage regulation in accordance with the transfer switch 7 in FIGS.1 and 2. The individual contactors 12 or relays are controlled viacontrol units 8 that are connected to a voltage regulator.

[0049] In accordance with FIG. 4, the partial windings 4 with theirtappings 5 are connected with a series of electronic switches 13, inparticular semiconductor switches, which carry out the voltageregulation in accordance with the transfer switch 7 in FIGS. 1 and 2.The individual semiconductor switches are controlled via electronicunits that are connected with the voltage regulator.

[0050] For form's sake, it is noted that for a better understanding ofthe invention the components are illustrated partly untrue to scaleand/or are enlarged and/or made smaller.

[0051] Moreover, individual features of the embodiment illustrated inthe figures in combination with other individual features or alone canrepresent independent solutions according to the invention inthemselves. In particular, the individual embodiments illustrated in thefigures can represent independent solutions according to the invention.The relevant tasks and solutions according to the invention are shown inthe detailed descriptions of these figures.

What is claimed:
 1. A method of regulating an electric voltage in anetwork node of at least one of electric supply networks and consumerunits, the method comprising: arranging a regulating transformer betweenthe network node and at least one end consumer, wherein the regulatingtransformer comprises a main winding and a regulating winding whichincludes switchable partial windings and a high leakage impedance;conducting a nominal current; switching the partial windings of theregulating transformer with a transfer switch; and short circuitingadjacent tappings of the partial windings, wherein the high leakageimpedance limits a ring current to an order of magnitude of the nominalcurrent during the short circuiting, and wherein the regulatingtransformer produces both an increase in voltage and a decrease involtage at the end consumer.
 2. The method of claim 1, wherein theregulating transformer is a longitudinal regulator.
 3. The method ofclaim 1, wherein the regulating winding is one of a concentric windingand a flat coil winding.
 4. The method of claim 1, wherein theregulating transformer is one of a full transformer and a one-coiltransformer.
 5. The method of claim 1, wherein the regulating winding isconnected to the main winding.
 6. The method of claim 1, wherein theregulating transformer further comprises a secondary winding and whereinthe regulating winding is connected to one of the main winding and thesecondary winding.
 7. The method of claim 1, wherein the regulatingtransformer is adapted to regulate voltages in the range of 10 kVA and10 MVA.
 8. An apparatus for regulating an electric voltage in at leastone of electric supply networks and consumer units, the apparatuscomprising: a regulating transformer arranged between a network node andat least one end consumer; the regulating transformer comprising a mainwinding and a regulating winding which includes switchable partialwindings and a high leakage impedance, the regulating transformerconducting a nominal current; and a transfer switch that switches thepartial windings of the regulating transformer, wherein adjacenttappings of the partial windings are adapted to short circuit such that,in an event of the short circuit, the high leakage impedance limits aring current which results from the short circuit to an order ofmagnitude of the nominal current, and wherein the regulating transformerproduces both an increase in voltage and a decrease in voltage at theend consumer.
 9. The apparatus of claim 8, wherein the regulatingtransformer is a longitudinal regulator.
 10. The apparatus of claim 8,wherein the regulating winding is one of a concentric winding and a flatcoil winding.
 11. The apparatus of claim 8, wherein the regulatingtransformer is one of a full transformer and a one-coil transformer. 12.The apparatus of claim 8, wherein the regulating winding is connected tothe main winding.
 13. The apparatus of claim 8, wherein the regulatingtransformer further comprises a secondary winding and wherein theregulating winding is connected to one of the main winding and thesecondary winding.
 14. The apparatus of claim 8, wherein the regulatingtransformer is adapted to regulate voltages in the range of 10 kVA and10 MVA.
 15. A method of regulating an electric voltage in a network nodeof at least one of electric supply networks and consumer units, themethod comprising: arranging a regulating transformer between thenetwork node and at least one end consumer, wherein the regulatingtransformer comprises a main winding and a regulating winding whichincludes switchable partial windings; conducting a nominal current;switching the partial windings of the regulating transformer with atransfer switch; short circuiting adjacent tappings of the partialwindings; and increasing a leakage impedance of the regulating winding,wherein the leakage impedance limits a ring current to an order ofmagnitude of the nominal current during the short circuiting.
 16. Themethod of claim 15, wherein the increasing results from a widenedleakage gap in the regulating transformer.
 17. The method of claim 15,wherein the regulating transformer produces both an increase in voltageand a decrease in voltage at the end consumer.
 18. The method of claim15, wherein the regulating transformer is a longitudinal regulator. 19.The method of claim 15, wherein the regulating winding is one of aconcentric winding and a flat coil winding.
 20. The method of claim 15,wherein the regulating transformer is one of a full transformer and aone-coil transformer.
 21. The method of claim 15, wherein the regulatingwinding is connected to the main winding.
 22. The method of claim 15,wherein the regulating transformer further comprises a secondary windingand wherein the regulating winding is connected to one of the mainwinding and the secondary winding.
 23. The method of claim 15, whereinthe regulating transformer is adapted to regulate voltages in the rangeof 10 kVA and 10 MVA.
 24. An apparatus for regulating an electricvoltage in at least one of electric supply networks and consumer units,the apparatus comprising: a regulating transformer arranged between anetwork node and at least one end consumer; the regulating transformercomprising a main winding and a regulating winding which includesswitchable partial windings and a widened leakage gap, the regulatingtransformer conducting a nominal current; and a transfer switch thatswitches the partial windings of the regulating transformer, whereinadjacent tappings of the partial windings are adapted to short circuitsuch that, in an event of the short circuit, the widened leakage gaplimits a ring current which results from the short circuit to an orderof magnitude of the nominal current, and wherein the regulatingtransformer produces both an increase in voltage and a decrease involtage at the end consumer.